It is no secret, that excess weight has been linked to 13 different types of cancer. The list goes from breast cancer, colon cancer, rectum, endometrial, esophageal adenocarcinoma, gallbladder, gastric, kidney, liver, multiple myeloma, ovary, pancreas and thyroid cancers. The role that sex hormones play as a result of excess weight has linkage to cancers that are hormone receptive such as breast and ovarian cancers. Inflammation at the cellular level due to excess weight as well as insulin resistance also plays a part.
Breast Cancer
One of the most common cancers in the United States and the leading cause of death in midlife among women, indeed many of us have had family members or someone we know affected by breast cancer. There is consistent evidence that excess weight and weight gain increase the risk of postmenopausal breast cancer. The Nurses' Health study followed women for 46 years and found that women who gained 25kg since the age of 18 had a risk increase of breast cancer in those who had never taken postmenopausal hormones. It's no surprise as fat tissue is a source of excess sex hormone estrogen store and leads to unopposed exposure increasing the risk of breast cancer. The weight related risk of breast cancer is higher among women who have not used any postmenopausal hormones.
Another study by Rosner in 2015 followed 77,000 women and found that among them a weight gain of 15 lbs. or more lead to a 40% higher risk of breast cancer in premenopausal women. Since pre-menopausal women are commonly affected by hormone receptor negative breast cancers, the risk of these cancers was higher in these women with gain of weight.
Colon Cancer
Colon Cancer is the third leading common cancer in the United States and the third most common cause of death. The studies show increasing BMI and waist circumferences, increasing risk of colon cancer with men higher in risk than women. A meta-analysis of 30 studies in 2007 found with every 5 unit increase in BMI the risk of colon cancer increased by 30%in men and 12% in women. Similar findings were found with waist circumference increase of 10cm.
Endometrial Cancer
One of the most common reproductive cancers in the United States with on average 60,000 women diagnosed yearly, excess weight has been linked to this cancer as well. Weight is a strong risk factor for type 1 endometrial cancer, which is most common and consist of endometrioid adenocarcinomas. There is a linear relationship of increase in relative risk of endometrial cancer type 1 with increasing BMI.
Gallstones
These are thought to be formed when excess cholesterol or not enough bile salts are present and the pain occurs when there is a failure of passage of one of these stones from the bile ducts. These leads to inflammation in the gallbladder and further can lead to inflammation in the liver or infection. The risk of gallbladder stones increases with BMI. The risk is relatively higher in women compared to men. Excess weight is linked to increased secretion of cholesterol into the bile, which is one way where weight may increase the development of gallstones.
Osteoarthritis
Osteoarthritis is a wear and tear disease of the cartilage of the joints over time particularly with aging and worsening with weight gain. In studies, adults with arthritis were reported as 16% with BMI less than 25. This number increases to 50% with a BMI greater than 25. That is a significant increase in arthritis in people with higher BMI and shows how obesity plays a part in development of arthritis.
Benign Prostatic Hyperplasia or BPH
Having central adiposity in men or increased weight circumference has been linked to increase incidence of both BPH and lower urinary tract symptoms such as urinary tract infections. In a Baltimore Longitudinal study it was found among men, those with waist circumference greater than 109cm compared to 89 cm, were twice as likely to develop BPH and have a prostatectomy. The central adiposity increases the estrogen to androgen ratio and sympathetic nervous system activity which is linked to BPH.
Nonalcoholic Fatty Liver Disease
Nonalcoholic fatty liver disease is increasing in incidence among those who do not drink alcohol or use moderation. Majority of folks have simple fatty livers but in some cases incidence of advancing liver disease is increasing to development of NASH or nonalcoholic steatohepatitis and cirrhosis. Liver cancer is the advanced stage of cirrhosis as a final result to liver injury. Statistic show that around 25% of adults in the United States have a diagnosis of NAFLD and among them 20% develop NASH which is about 5% of adults in the United States. That is a big number.
Obesity is an important risk factor to the development of fatty liver disease, and as the rates of obesity increase in the United States, it is not a surprise that this number is also going up. Obesity associated insulin resistance or diabetes, inflammation and dyslipidemia are the key contributors to the development of NAFLD and NASH.
Infertility
In the United States, among married women aged 15 to 49 years with no prior births, about 1 in 5 (19%) are unable to get pregnant after one year of trying (infertility). Also, about 1 in 4 (26%) women in this group have difficulty getting pregnant or carrying a pregnancy to term (impaired fecundity). This is according to the CDC's website. In a Nurses' Health Study in 2002, the author estimated that a quarter of the rates of infertility were linked to being overweight and obesity.
Discrimination and Lifestyle
Studies are showing that overweight folks and obese individuals are less likely to be promoted. They also show that overweight and obese also face increasing discrimination at work particularly women. A study done in Copenhagen showed that compared to similar folks at each level of educational level the social class was lower for those with overweight or obesity diagnosis, even though educational level were the same. Furthermore, studies also showed that men and women who were obese were less likely to get married than those who were in normal BMI.
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